GCC 4.4.0 on Windows does not like the format %zu. It is quite unlikely,
though, that we need more merge bases than a %d can display, so replace
the %zu by a %d.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Steffen Prohaska <prohaska@zib.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>